Scott Plasma Size Guide: Plasma RC and Plasma RC TT

Scott labels the Plasma with a letter and a number together, from XS/49 up to XL/58, and the number is a nominal frame size rather than a tube measurement. Five sizes cover the range. What sets the Plasma apart is that Scott publishes pad stack and pad reach ranges for every size, which is the data that actually decides whether a time trial bike fits. Browse the Plasma collection or the full Scott range at Bikeroom.

Please note. The size suggestions below are indicative. They are a starting point built on official geometry and average body proportions, not a guarantee of fit. Scott itself points buyers at its Smartfit tool rather than a height chart, and a bike fitter will beat both. Confirm your size with a professional fit, or with our team, before you buy.

Why a time trial size is not your road size

On a road bike, frame stack and reach roughly describe where your hands go. On a time trial bike they do not, because your weight sits on the arm pads. The numbers that set the position are pad stack and pad reach, measured from the bottom bracket to the pad. Frame stack and reach only tell you where the cockpit can start from.

Seat tube angle is the second difference. Road race frames sit near 73 degrees. Time trial and triathlon frames run from roughly 76 to 80 degrees, which rotates the pelvis forward and keeps the hip angle open once the torso drops. Scott holds the Plasma at 75.2 degrees in every size, which is at the shallow end of that band and part of why the frame suits long distance as well as short.

The third is that many riders sit a size below their road size, because the front end has to come down and the pads reach out in front of the head tube. Our Scott road bike size guide is the reference for the road side of that comparison.

The fourth is the rulebook. UCI article 1.3.013 requires the tip of the saddle to be at least 5 cm behind a vertical plane through the bottom bracket. A morphological exemption is available on request. The rules also cap how far the extensions may reach forward. Non-drafting triathlon has no equivalent limit, so a triathlete can run the saddle further forward. The split is covered in our guide to time trial bikes versus triathlon bikes.

Quick size finder

Find your height, cross check your inseam, then look at the pad stack range for that size. If your current pad height sits outside the range, the size is wrong whatever the height row says.

XS/49 and S/52 share the same 520 mm frame stack and the same pad stack range. They differ by 20 mm of reach, so choose between them on torso and arm length, not on height.

How to measure yourself

Height. Stand barefoot against a wall with your heels together, looking straight ahead. Rest something flat on your head, level against the wall, mark the point and measure from the floor.

Leg length (inseam). Barefoot, feet about 15 cm apart, press a book up between your legs as if it were a saddle. Hold it level against the wall, mark the top edge and measure from the floor. This drives saddle height and standover.

Pad stack and pad reach. If you already ride a time trial bike, measure from the centre of the bottom bracket. Go vertically to the top of the arm pad, then horizontally to the centre of the pad. Those two numbers compare directly with Scott's published ranges, and are worth more than any height chart.

Plasma RC (triathlon and time trial)

The Plasma RC is the frame under Scott's Plasma RC Pro and the framesets sold alongside it. Five sizes, a 75.2 degree seat tube angle, a 72.5 degree head tube angle and chainstays that adjust between 403 and 413 mm. The cockpit is the Syncros Creston iC TT. Scott offers it with basebars in 85, 105 and 125 mm, a mast adjustable from 0 to 145 mm, extension tilt from 0 to 15 degrees and grip angle between 13 and 53 degrees.

Official Scott geometry, read on scott-sports.com in September 2026 and identical to the Plasma RC geometry chart Scott published in 2022. Scott does not publish a rider height range per size and points buyers at its Smartfit tool instead.

The pad ranges are the useful part. Every size gives 120 mm of pad height adjustment and roughly 138 mm of pad reach adjustment, which is a wide window. Two adjacent sizes overlap heavily on pad stack, so the real decision between them is reach.

Plasma RC TT (UCI time trial frameset)

Scott describes the Plasma RC TT as a UCI legal time trial and triathlon bike aimed at WorldTour riders. It claims a 12 per cent weight reduction against the previous generation and 33 seconds saved over a 40 km course at the same power, both manufacturer figures measured against their own predecessor. Scott lists the frameset in three sizes.

Scott does not publish a geometry chart specific to the Plasma RC TT. The chart on one frameset page repeats the five size Plasma RC table above, which cannot describe a three size frame, and the HMX version of the same frameset returns "Geometry not available". Measure the actual frame or ask the seller.

That gap matters. Slowtwitch reported at launch that the RC TT replaced the Plasma 5 TT and is built for time trial racers rather than long course Ironman use, so it is not simply a relabelled Plasma RC. Treat the two as different frames until Scott publishes numbers that say otherwise.

What riders say about Plasma sizing

The consistent note in the coverage is adjustability rather than frame size. Slowtwitch, reviewing the RC TT in May 2023, singled out how narrow the armrests can be set and how far they move up, down and outward. BikeRadar's Jack Evans logged the same cockpit range at launch, down to the three basebar lengths and the 0 to 30 mm of grip length adjustment.

The second note is that the published pad ranges are wide enough to blur the size boundaries. Because adjacent sizes overlap by a large margin on pad stack, riders who use the chart properly tend to end up choosing on reach and on how much of the seatpost they want showing.

The third is the seat tube angle. At 75.2 degrees the Plasma is shallower than several rivals in the 78 to 80 degree range. Triathletes coming from a steeper frame may need to push the saddle forward on its rails to recreate their position.

Between two sizes?

Go smaller for a lower, shorter, sharper position and quicker handling, especially for short time trials and technical courses. Go larger for stability and long distance, and if your pads already sit high on your current bike. A long torso and long arms point up a size, long legs and a short torso point down one.

With the Plasma, check the pad reach range before the frame stack. If your target pad reach sits within 20 mm of the end of a size's range, take the size that puts it nearer the middle. If you are buying pre-owned, our practical guide to buying a used triathlon bike covers what else to inspect.

Shop Scott time trial bikes at Bikeroom

• Scott Plasma for the Plasma RC and Plasma RC TT in stock
• Time trial and triathlon bikes for the whole category across brands
• New triathlon bikes if you want a current model year
• Triathlon framesets if you already have the groupset and cockpit

If you know your pad stack and pad reach and want to check them against a specific Plasma before you commit, send the numbers over and talk to our concierge.

Disclaimer: the size suggestions in this guide are indicative only and given in good faith as general guidance. Stack, reach and pad range figures are official Scott data for the model generations named, read in September 2026, and can change between model years. The rider height and inseam bands are Bikeroom's own reading of that geometry, not manufacturer data. Always confirm against the specific bike you are buying and, where possible, with a professional fit.

Sources: scott-sports.com Plasma RC Pro geometry chart; BikeRadar, Jack Evans, 4 May 2023; Slowtwitch, Dan Empfield, 5 May 2023.